Aim This study aims to assess the impact of climate change on forests and vascular epiphytes, using species distribution models (SDMs).Location Island of Taiwan, subtropical East Asia.Methods A hierarchical modelling approach incorporating forest migration velocity and forest type-epiphyte interactions with classical SDMs was used to model the responses of eight forest types and 237 vascular epiphytes for the year 2100 under two climate change scenarios. Forest distributions were modelled and modified by dominant tree species' dispersal limitations and hypothesized persistence under unfavourable climate conditions (20 years for broad-leaved trees and 50 years for conifers). The modelled forest projections together with 16 environmental variables were used as predictors in models of epiphyte distributions. A null method was applied to validate the significance of epiphyte SDMs, and potential vulnerable species were identified by calculating range turnover rates. ResultsFor the year 2100, the model predicted a reduction in the range of most forest types, especially for Picea and cypress forests, which shifted to altitudes c. 400 and 300 m higher, respectively. The models indicated that epiphyte distributions are highly correlated with forest types, and the majority (77-78%) of epiphyte species were also projected to lose 45-58% of their current range, shifting on average to altitudes c. 400 m higher than currently. Range turnover rates suggested that insensitive epiphytes were generally lowland or widespread species, whereas sensitive species were more geographically restricted, showing a higher correlation with temperature-related factors in their distributions.Main conclusions The hierarchical modelling approach successfully produced interpretable results, suggesting the importance of considering biotic interactions and the inclusion of terrain-related factors when developing SDMs for dependant species at a local scale. Long-term monitoring of potentially vulnerable sites is advised, especially of those sites that fall outside current conservation reserves where additional human disturbance is likely to exacerbate the effect of climate change.

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The distribution of species on mountains has been related to various predictor variables, especially temperature. Thermal specializationpresumed to be more pronounced on tropical mountains than on temperate mountains-accounts for the elevational pattern of species richness and varies between organisms and geographic areas. In this study, the elevational and regional distribution patterns of 331 epiphyte species in Taiwan were explored using 39,084 botanic collections, mostly from herbaria. Species richness showed a peak in elevation at 500-1500 m. This peak could not be explained by a null model, the mid-domain effect, suggesting that environmental variables accounted mostly for the distribution of species on the mountains. Next, species distributions were modeled to assess epiphyte regional and elevational distribution patterns. The model results not only corroborated the position of the mid-elevation peak in richness, but also identified two mountain areas on the island with exceptionally high species richness. These areas of high epiphyte diversity coincide with areas of high rainfall in relation to the direction of the prevailing winds. Moreover, a subsequent exploratory ordination analysis showed a varied thermal preference between epiphyte subcategories (hemiepiphytes, dicotyledons, orchids, and ferns). In contrast to predictions by the elevational Rapoport's rule, ordination analysis also showed that the degree of thermal specialization increased with elevation, suggesting that highland species may be especially vulnerable to global warming.Abstract in Taiwanese is available in the online version of this article.

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